The overall objective is to understand how gene expression is regulated during spore formation and to understand how gene expression relates to the morphological changes during spore formation. Two interconnected approaches will be pursued towards this objective. The first is to continue analysis of two loci, spoIIA and spoVA, that are associated with major morphological events during spore formation: septum formation, engulfment of the prespore by the mother cell, and assembly of the protective layers around the prespore. The spoIIA locus is transcribed first as a 1.7 kb RNA; this region includes the gene for an RNA polymerase sigma factor. It is proposed to analyze the control of its transcription, identifying the factors involved and defining their targets of action in the region 5' to the transcript. The relationship of 1.7 kb transcript formation to septum formation will be investigated. The spoIIA locus is later transcribed from an upstream promoter as a 2.9 kb species at about the time of engulfment; the large transcript encodes a penicillin-binding protein which could be involved in formation of the cortex, a protective layer surrounding the spore protoplast. It is proposed to investigate the identity and function of this penicillin-binding protein. It is proposed to analyze the regulation of the 2.9 kb transcript and to relate its expression to that of other late-expressed sporulation loci. The spoVA locus is expressed exclusively in the prespore after engulfment. It is proposed to test if this compartmentalization is necessary for spore formation, and to investigate the determinants of compartmentalization. The second approach is to identify genes that are essential for vegetative growth and are also under sporulation-specific control. This class of gene has largely been neglected in studies of spore formation. However, there are likely to be a substantial understanding of spore formation. We will identify and study essential genes controlled directly or indirectly by spoIIA. We are particularly interested in essential genes that might be required for septum formation, and will investigate possible roles of ftsA and ftsZ in sporulation.